This invention relates to a method and improved apparatus for locating data of interest in conjunction with a diagnostic method of characterizing blood flow through the heart. More specifically, it relates to the use of an improved adjustable cursor control circuit for locating data of interest on a cathode ray tube display.
Conventional methods of locating data of interest on a cathode ray tube display such as the joystick, track ball and light pen, are generally limited to defining the x-y coordinates of a single point on the face of the cathode ray tube display. Generally, they do not have the capability to define a moveable cursor line on the face of the cathode ray tube display.
More sophisticated hybrid methods combining hardware and software techniques may be utilized to generate moveable cursor lines; however, many of these conventional systems utilize some form of analog to digital conversion which has an inherent instability of one-half the least significant bit (LSB). In the absence of corrective techniques this inherent instability usually appears as unwanted jitter on the cursor lines. In high resolution applications the effect of jitter is clearly undesirable.
An example of a high resolution system where the effect of jitter on the cursor lines is undesirable is illustrated in copending application Ser. No. 854,537, filed Nov. 25, 1977, entitled "Method and Apparatus for Characterizing Blood Flow through the Heart," assigned to the assignee of the present invention, and incorporated herein by reference. by providing the user with a stable method of locating data of interest on a cathode ray tube display the diagnosis and monitoring of patients is enhanced.
Accordingly, it is an object of the invention to provide a method for locating data of interest on a cathode ray tube display in conjunction with a diagnostic method of characterizing blood flow through the heart.
It is a further object of the invention to provide improved apparatus for locating data of interest on a cathode ray tube display in a system for characterizing blood flow through the heart.
It is still a further object of the invention to provide apparatus capable of generating a plurality of stable horizontal or vertical cursor lines to locate data of interest on a cathode ray tube display.
Another object of the invention is to provide a low cost adjustable cursor control circuit for locating data of interest on a cathode ray tube display.